急！jsp javascript验证表单

各位高手 帮小弟看看 什么地方出现了错误 点击注册后什么反应都没有啊 <%@ page contentType="text/html; charset=utf-8" language="java" import="java.util.*" pageEncoding="GBK"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>register</title>
    <style type="text/css">
<!--
     -->
     </style>
     <script language="javascript" type="text/javascript">
     function ger_code(code_length) {
     var rand_aa="";
     var code=new Array("0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F","G","H","I","J",
     "K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","a","b","c","d","e","f","g","h",
     "i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","!","@","#","$","%","&",
     "*","(",")","-","_","|","?","/");
     var code_Num=code.length;  //数组长度
     for(i=0;i<code_length;i++)
    {
     var ran_ss=parseInt(Math.random()*code_Num);
     rand_aa+=String(code[ran_ss]);
    }
      document.write("&nbsp;<input type="text" name="check_code"  size="+code_length+" value="+rand_aa+" class=blank_bg maxsize=5 readonly=true >" );
    }
     function checkForm()
     {
       var username = document.getElementById("username").value;
       var num = document.getElementById("num").value;
       var xueyuan = document.getElementById("xueyuan").value;
       var ps1 = document.getElementById("password").value;
       var ps2= document.getElementById("password1").value;
       var check = document.register.checkCode;
        if(username.length==0)
        {
           alert("请填写姓名！");
           return false;
        }
        else if(num.length==0)
        {
           alert("请填写学号！");
           
           return false;
        }
        else if(xueyuan.length==0)
        {
           alert("请填写所属学院！");
           
           return false;
        }
        else if(major.length==0)
        {
           alert("请填写专业！");
           
           return false;
        }
        else if(ps1.length==0)
        {
           alert("请填写登陆密码！");
           
           return false;
        }
        else if(ps2.length==0)
        {
           alert("请填写重复密码！");
           
           return false;
        }
        else if(num.length<8)
        {
           alert("请正确填写学号信息！");
           
           return false;
        }
        else if(ps1.length<6||ps2.length<6)
        {
           alert("密码不能小于6位数！");
           
           return false;
        }
        else if(ps1!=ps2){
           alert("两次输入的密码不一致，请重新输入！");
           
           return false;
        }
        else if(check.value != register.check_code.value){
           alert("验证码不正确");
           
           return false;
        }
        return true;
      }    
     </script>
  </head> 
   
  <body>
    <form name="register" id="register" method="post" action="" onsubmit="return checkForm();"><div align="center">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
      <strong><h1>欢迎光顾教务处选课系统！</h1></strong><div align="left"><div align="left">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 带<font size = "5" color = "red">*</font>为必填</div><table width="800" height="185">
   <table width="550" height="155" border=1 align="center"> 
<tr>
<td width="100" height="47" bgcolor=yellow><div align="right" class="STYLE4"><font size = "5" color = "red">*</font>姓名：</div></td> 
<td width="398"><input type="text" size=20 name="username" id="username"></td> 
</tr><tr>
    <td height="47" bgcolor=yellow>
     <div align="right"><font size = "5" color = "red">*</font>性别：
     </div>
    </td>
    <td>
     <label>
      <input type="radio" name="radio" id="radio" value="boy" />
      男
      <input type="radio" name="radio" id="radio2" value="girl" />
      女       </td> 
     </label>
    </td>
   </tr>
<tr>
<td height="45" bgcolor=yellow><div align="right" class="STYLE4"><font size = "5" color = "red">*</font>学号：</div></td> 
<td><input type="text" size=20 name="num" id="num">（8位数字）</td> 
</tr>
<tr>
<td height="45" bgcolor=yellow><div align="right" class="STYLE4"><font size = "5" color = "red">*</font>学院：</div></td> 
<td><select name="xueyuan" id="xueyuan" class="select" onchange="goSelect(5);">
      <option value="null" selected="selected">
       请选择学院
      </option>
      <option value="1">
       材料冶金学院
      </option>
      <option value="2">
      机械学院 
      </option>
      <option value="3">
       工商管理学院
      </option>
      <option value="4">
       软件学院
      </option>
      <option value="5">
       信息学院
      </option>
      <option value="6">
       资源与土木工程学院
      </option></td> 
</tr>
<tr>
<td height="45" bgcolor=yellow><div align="right" class="STYLE4"><font size = "5" color = "red">*</font>专业：</div></td> 
<td><input type="text" size=30 name="major" id="major"></td> 
</tr>   
<tr>
<td height="45" bgcolor=yellow><div align="right" class="STYLE4"><font size = "5" color = "red">*</font>密码：</div></td> 
<td><input type="text" size=30 name="password" id="password">（不小于6位数字）</td> 
</tr>
<tr>
<td height="45" bgcolor=yellow><div align="right" class="STYLE4"><font size = "5" color = "red">*</font>确认密码：</div></td> 
<td><input type="text" size=30 name="password1" id="password1">（不小于6位数字）</td> 
</tr>
<tr>
<td height="45" bgcolor=yellow><div align="right" class="STYLE4"><font size = "5" color = "red">*</font>验证码：</div></td> 
<td><input type="textarea"  name="checkCode" ><script language = "javascript">ger_code(5);</script></td> 
</tr>
<tr align=center><td colspan=2><input type="submit" name="submit" value="注册 " > 
<input type="reset"  name="reset" value="重置"></td> 
</tr> 
</table>
</form>
</body>
</html>